Two Indian sailors were found dead Thursday a day after the submarine they were on filled with toxic smoke , authorities said .

The accident , the latest in a series of problems plaguing the Indian fleet , prompted the chief of the country 's navy to resign .

Seven crew members of the Russian-built submarine , the INS Sindhuratna , have been hospitalized after inhaling smoke emanating from one of the vessel 's compartments early Wednesday while it was off the coast of Mumbai , the navy said .

Two other sailors on the submarine had been reported missing . Their bodies were found Thursday in a smoke-affected compartment of the vessel , authorities said .

Adm. D.K. Joshi , the navy 's chief of staff , stepped down Wednesday after news of the problems on the submarine emerged , the government said .

Joshi took `` moral responsibility for the accidents and incidents which have taken place during the past few months , '' the defense ministry said in a statement .

The Indian navy declined to provide an exact number of how many incidents had taken place on vessels in recent months , saying only that there had been `` a couple of serious accidents involving submarines . ''

In August , an explosion and fire sank another of India 's Russian-made submarines , the INS Sindhurakshak , killing all 18 sailors on board . That was the navy 's deadliest peacetime disaster .

The cause of the smoke Wednesday on the Sindhuratna is still under investigation , the navy said .

The Indian navy has been struggling to modernize its aging submarine fleet , which , like much of the Indian military , relies heavily on Russian hardware .

Analysts say the current number of submarines is far fewer than India needs to patrol is lengthy coastline , but plans to update the fleet have been held up because of technical problems , bureaucracy and higher-than-expected costs .

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Two sailors who were missing are found dead , authorities say

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Seven other sailors are hospitalized after toxic smoke on a submarine

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The chief of the navy has stepped down following a series of problems on vessels

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In August , an explosion on another Indian submarine killed all 18 sailors on board